1. Field
The invention is in the field of attachments and couplings for the ends of pipe wherein the end portion of a pipe to be coupled to or attached to has a circumferential shoulder inwardly from the end of the pipe, usually formed by a circumferential groove in the pipe, which mates with the attachment or coupling to secure it to the pipe and prevent axial movement of the pipe with respect to the attachment or coupling.
2. State of the Art
There are many ways of attaching pipes to valves, connectors or other fittings and for coupling the ends of pipe together. It is common to provide screw threads on the ends of pipes with mating screw threads on valves, connectors, or other fittings, or to connect threaded ends of pipe together with a threaded coupling. With plastic pipe, the various fittings may slide over the outside of the pipe and be glued into place or slide into the end of the pipe and be clamped into place.
It has also become common in some applications to provide grooves in the end portions of pipe to be connected together and to then connect the pipes with a clamp having flanges or keys which fit into the grooves to restrain axial movement of the pipes. Rather that fitting into a groove in the end portions of the pipes, these couplings can also fit against the side of a raised shoulder or bead at the end of a pipe. Such fittings are sold by Victaulic Company of America, Easton, Pa. and are shown in U.S. Pat. Nos. 3,695,638; 3,761,114; 4,471,979; 4,561,678; 4,522,434; 4,611,839; 4,639,020; and 4,896,902. Generally these couplings extend between and engage the grooves on the ends of pipe to be joined end-to-end with a gasket held by the coupling around the abutting ends of the pipe to prevent leakage therefrom. The couplings are generally formed of two arcuate pieces, each adapted to extend circumferentially around half the pipe with the pieces joined and tightened or clamped around the pipe by bolts extending through outwardly extending bolt pads. With such attachment, the bolts securing the arcuate pieces of the coupling together around the pipe constrain the pressure of the fluid flowing in the pipe. Also, if the pieces of the coupling do not come completely together because of normal variations in the outside diameter of the pipes being joined, the sealing gasket may be left exposed or uncovered between the pieces which can result in extrusion of the gasket between the pieces and possible leakage. Placement of the coupling pieces over the pipe ends to join the pipes requires both pipe ends to be held in substantially exact position with the pipes aligned end-to-end and with grooves properly spaced to receive the keys or flanges of the coupling pieces as the coupling pieces are placed around the pipes and tightened therearound. This will usually require two workmen to accomplish. While such couplings usually extend between the grooves of pipes to be joined, in some instances, such as shown in U.S. Pat. No. 3,761,114, one of the pipes to be joined has the groove formed in the end portion thereof and the coupling engages the groove of that pipe end and is joined in more conventional manner, such as by a flange attachment, to the other pipe end, or to some type of pipe fitting. Still, however, the couplings are in two pieces joined by bolts, and require assembly in the field.